To facilitate transportation, packing and carrying, the handlebar assembly of electrobicycle or ordinary bicycle is generally designed to be of foldable structure. The current means of folding the handlebar assembly of an electrobicycle or ordinary bicycle is generally to hinge the front fork tube and then to fix them by tightening screws. Although folding of the handlebar assembly can be achieved in this way, yet in operation, tools must be used to amount and dismount the screws in order to proceed the folding. The folding is not only troublesome but also time-consuming. Additionally, when the handlebar assembly is folded in this way, the direction of folded handlebar can not be changed to the same direction of the bicycle body. As a result, only the height of the bicycle can be decreased, but the width of the bicycle body and whole dimension of its package are still rather bulky.